We will investigate the toxicity of tributyltin, (the active ingredient in antifouling paints used extensively on boats in the recent few years) on a common species of shallow water estuarine fish. The limited number of studies that have been performed on estuarine invertebrates indicate that this chemical is extremely toxic. We will investigate its effects on the mummichog or killifish, Fundulus heteroclitus. We will initially ascertain toxic levels (LC 50) for larvae and adults, then investigate sublethal effects on embryonic development, growth (Fin regeneration) and behavior (ability to capture prey). We will also measure the ability of this fish to concentrate and accumulate this metal from water and from food to get an indication of the potential of this metal to bioaccumulate and undergo food chain amplification. Since tributyltin (TBT) is an organometallic compound like methylmercury and is neurotoxic in mammals like methylmercury, it may, like methylmercury, have the ability to undergo food chain amplification, and thus pose a threat to human consumers of seafood.